The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to deposit and etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and radio frequency (RF) plasma may be used to activate chemical reactions.
Shallow trench isolation (STI) features provide electrical isolation between individual transistor devices in integrated circuits (ICs). The STI features may be filled with dielectric film such as flowable oxide that is deposited using flowable chemical vapor deposition (FCVD) or other methods. The flowable oxide provides liquid-like filling behavior.
The quality of the flowable oxide film is limited by high silanol content, which makes the flowable oxide film porous. The silanol bonds in the flowable oxide film are removed by annealing in a high temperature furnace, exposure to UV treatment or plasma annealing. The effectiveness of each of these approaches is limited due to low thermal budgets and poor penetration depth into the flowable oxide film. Conventional plasma annealing cannot be used due to a high sputtering rate, which damages the film.
In some applications, an aspect ratio (AR) of the trench can be as high as 8:1 and an opening of the trench may narrow down to about 20 nm. Achieving void-free STI fill is important because the film may be subjected to further processing during subsequent integration steps. The subsequent processing may expose the voids. In some examples, the voids may be unintentionally filled with conductive material, which can lead to short circuits.
The densification process should be able to achieve a fully densified film down to a bottom portion of the trenches or to a point where wet chemicals may reach during subsequent chemical mechanical polishing (CMP) or other wet integration steps.